Method and apparatus for joining at least two plastic parts

ABSTRACT

Method and apparatus for joining at least two plastic parts.A method for joining at least two plastic parts (1, 5) along a predeterminable common joining point using infrared radiation (IR), is characterized in that each of the plastic parts (1, 5) to be joined is heated using infrared radiation at least along the joint by means of an assignable radiation source without touching the respective other plastic part (1, 5), that the respective one radiation source is operated independently and spatially separated from at least one further radiation source, that the radiation sources emit their respective infrared radiation to the respective assignable plastic part (1, 5) without contact and following the contour of the joint, and that the degree of heating by means of the respective infrared radiation is selected such that the joint is formed when the plastic parts (1, 5) are brought together.

The invention relates to a method for joining at least two plastic parts along a predeterminable common joining point using infrared radiation. The invention also relates to an apparatus for performing such a process.

In the manufacture of plastic containers for food, for cosmetics or for medical purposes, in particular parenterals or substances for parenteral nutrition, it is generally necessary to attach functional elements to the container concerned in a microbiologically sealed manner and avoiding particulate contamination. In the state of the art, sealed welded joints are produced for this purpose by using welding processes, for example vibration welding, friction welding or ultrasonic welding. However, the disadvantage at this is the generation of particles due to the friction that immanent in of the welding process. Contamination due to friction also occurs during hot-plate welding, known per se, when the components to be welded come into contact with the heating plate. Furthermore, this process can result in deposits being formed, which can strongly influence the welding quality.

WO 2005/080067 A2 discloses a welding method for joining plastic parts, in which the parts to be welded are brought into contact and then are heated using infrared radiation and are welded together. Because the parts to be joined are brought into contact with each other in a cold state, the risk of particle formation cannot be excluded in this case as well. Furthermore, the process shown in this document is limited to components of simple geometry. DE 20 2006 003 323 U1 discloses a further process for infrared welding of plastic parts. However, this process is limited to the spot welding of relatively thin, large-area parts only and does not allow a microbiologically sealed weld joint.

Based on this state of the art, the invention addresses the problem of specifying a method permitting the production of sealed welded joints of plastic parts without microbiological contamination and without the risk of particle formation.

According to the invention, this object is achieved by a process having the features of claim 1.

According to the characterizing part of claim 1, an essential feature of the invention is that each of the plastic parts to be joined is heated using infrared radiation at least along the joint using an assignable radiation source without touching the respective other plastic part, that the respective one radiation source is operated independently and spatially separated from at least one further radiation source, that the radiation sources emit their respective infrared radiation to the respective assignable plastic part without contact and following the contour of the joint, and that the degree of heating by means of the respective infrared radiation is selected such that the joint is formed when the plastic parts are brought together. Because heating is performed close to the contour of the joint, but without contact, parts having a special geometry can also be heated at the joint with a temperature that is optimal for the welded joint, such that, when the parts are brought together, the welded joint is formed without microbiological contamination and free of particles.

The connection point can be formed as a linear connection seam, and the respective plastic parts can be joined applying a predeterminable contact pressure on these parts.

Advantageously, the respective radiation source is formed by an IR radiation element, wherein the IR radiation elements used are operated at different temperatures, preferably an element at temperatures of 380° C. to 480° C., particularly preferably 400° C. to 450° C., and a respective other element at temperatures of 450° C. to 600° C., particularly preferably 500° C. to 550° C., at a heating time to the respective plastic part of preferably approximately 4 seconds.

In this case, a cooling device is used to cool plastic parts that are heat-sensitive due to the material and/or geometry.

It is particularly advantageous when using the method according to the invention, that at least a plastic part is produced as a filled and closed container by a blow-molding, filling and sealing process.

Advantageously, the filled container is closed by a head membrane and enclosed by a ring-shaped neck collar at its neck part, which collar is connected to a cap placed on the container on the side of its head membrane and forming the plastic part via a ring web of the cap along the connecting seam, whereas the container is used as the other plastic part for the joining or welding process.

Particularly advantageously, a preferred spacing between the ring web of the cap and one assigned IR radiation element is selected to be between 0.2 mm and 0.6 mm and the spacing between the neck collar of the container and the other assigned radiation element is selected to be between 0.4 mm and 0.8 mm.

Preferably, the infrared radiation generated by the respective radiation source respectively radiation element is emitted broadband and multidirectionally.

Particularly advantageously, the head membrane of the container is heated in a manner reducing the germ count but without melting for joining cap and container.

The joining of cap and container is performed in a low-particle way advantageously by using different IR radiation sources or IR radiation elements.

According to patent claim 11, the subject matter of the invention is also an apparatus for performing a process according to one of claims 1 to 10, which is characterized in that the respective radiation source is formed by an IR radiation element arranged inside an respective heating element assigned, which follows the contour of an assignable plastic part to be irradiated without contact.

Advantageous embodiments of the apparatus are specified in the further dependent claims 12 to 18.

According to claim 19, the subject matter of the invention is further a container, which is preferably produced by a blow molding, filling and sealing (BFS) process and is connected to a cap using a method according to any one of claims 1 to 10 and/or a apparatus according to any one of claims 11 to 18.

The invention is explained in detail with reference to the drawings below.

In the drawings:

FIG. 1 shows a perspective oblique view of a plastic part in principally schematic form of a cap according to the state of the art, which can be attached to the neck collar of a plastic container by welding;

FIG. 2 shows an oblique perspective view of a partial representation of an infusion container according to the state of the art, to the neck collar of which the cap of FIG. 1 can be attached;

FIG. 3 shows a perspective oblique view of an infrared radiation element;

FIG. 4 shows a vertical section of a cap heating element comprising the IR radiation element of FIG. 3 and the cap of FIG. 1 exposed to the radiation of the IR radiation element;

FIG. 5 shows an enlarged partial section of the area designated by V in FIG. 5;

FIG. 6 shows a perspective oblique view of the cap heating element of FIG. 4, viewed in the direction of the IR radiation element;

FIG. 7 shows a perspective oblique view corresponding to FIG. 6, but with the assigned cap of FIG. 1, which cap is to be exposed to IR radiation;

FIG. 8 shows a perspective oblique view of an infrared radiation element of a container heating element;

FIG. 9 shows a schematically simplified vertical section of the container heating element containing the IR radiation element of FIG. 8 and of the upper part of the container of FIG. 2, the neck collar of which is exposed to the radiation of the IR radiation element;

FIG. 10 shows an enlarged partial section of the area designated by X in FIG. 9;

FIG. 11 shows a perspective oblique view of the container heating element having the IR radiation element of FIG. 8, viewed in the direction of the IR radiation element; and

FIG. 12 shows a perspective oblique view of the container heating element of FIG. 11 and the upper end area of the container of FIG. 2, which is exposed to IR radiation in the area of its neck collar.

With reference to the drawing, the invention is described in more detail by means of an exemplary embodiment, in which a cap 5, which is shown separately in simplified form in FIG. 1 and which is an infusion cap in accordance with DIN ISO 15759 made of plastic, is attached to the neck collar 2 of a container 1 by infrared welding. In this case, the container 1 is an infusion container having a head and neck area in accordance with DIN ISO 15759, which is manufactured, filled and sealed according to the known BFS procedure. It goes without saying that the invention advantageously is equally applicable to the joining of different kinds of plastic parts by welding using infrared radiation.

As most clearly shown in FIG. 2, the container 1 has a radially projecting neck collar 2 adjoining its container neck part 3, which neck collar 2 forms the joint on the container side for the welding process, to which joint, see FIG. 4, a ring web 6 projecting axially at the opening edge of the cap 5 can be welded, which web 6 forms the joint at the cap side. When the cap 5 is attached to this common joint, there is a thin and sensitive head diaphragm 4 forming the closure of the tank 1 at the head side protected inside the cap 5. For the welding process, the cap 5 and the container 1 in the area of its neck collar 2 are each individually heated without contact to the welding temperature by means of infrared radiation. Therefore, for the cap 5, is provided a cap heating element 14 a, which is shown in FIGS. 4 to 7 and which has an IR radiation element 7 a exposed at one end face, which is attached to an insulation body 8 a by means of drilled mounting holes 9 and can be supplied with power by an electrical connection 10. As most clearly shown in FIGS. 4 and 5, the IR radiation element 7 a has the shape of a stepped cylindrical disc, which, for heating the ring web 6 of the cap 5 using IR radiation, has two radiation surfaces 11 a and 11 b arranged in a stepped manner relative to one another, of which the radiation surface 11 a forms a horizontal ring surface and the radiation surface 11 b forms a vertical ring surface. During the heating process the cap 5, as FIGS. 4 and 5 show, is held such that the radiating surfaces 11 a, 11 b extend closely along the contour of the ring web 6, but are held by the latter without contact, wherein the preferred spacing between the ring web 6 and the surfaces 11 a, 11 b of the radiating element 7 a is 0.2 mm to 0.6 mm. FIG. 7 shows the arrangement of the cap 5 in this position on the cap heating element 14 a.

FIG. 8 shows a separate illustration of an IR radiation element 7 b, that is attached to the free end face of a container heating element 14 b for heating the container 1, which at its neck collar 2 is shown in FIGS. 9 to 12. The IR radiation element 7 b is provided for the container 1 and has the shape of a ring body having stepped inner surfaces forming radiating surfaces 11 c, 11 d and 11 e, which are held close, but without contact, to the contour of the area of the neck collar 2 of the container 1 during the heating process, as shown in FIG. 9 and most clearly in FIG. 10. As shown, the radiating surface 11 e forms a horizontal ring surface, the radiating surface 11 c forms a ring surface inclined at an angle of 45° thereto and the radiating surface 11 d forms a vertical ring surface. As FIGS. 9, 11 and 12 show, the container heating element 14 b has two insulation bodies 8 b and 8 c, of which the insulation body 8 b has the form of an annular body, on which the IR radiation element 7 b surrounds one ring opening and the other ring opening is closed by the other insulation body 8 c, which forms an end plate. During the heating process, the IR radiation element 7 b is held by the insulation body 8 b to the neck collar 2 of the container 1 in a contact-free manner as shown in FIGS. 9 and 10, wherein the head diaphragm 4 of the upper end part of the container 1 extends into the interior space formed by the insulation body 8 b, which is closed at the top by the second insulation body 8 c. As FIG. 9 shows, in this position the head diaphragm 4 is at a minimum spacing from the insulation bodies 8 b and 8 c, which is 5 mm, preferably 8 mm and particularly preferably 10 mm. The distance between the radiation surfaces 11 c, 11 d and 11 e and the neck collar 2 is set to a minimum, typically in the range of 0.4 mm to 0.8 mm.

For the heating process, the IR radiating elements 7 a and 7 b are preferably set to different temperatures, which are in the range of 380° C. to 480° C. for the radiating element 7 a and 450° C. to 600° C. for the IR radiating element 7 b, wherein the typical heating time is approx. 4 seconds. To only superficially heat the very thin and thus thermally sensitive head diaphragm 4 of the container 1 and in that way germ count reducing without causing any damage, for instance due to melting, when the neck collar 2 of the container 1 is heated an active and controlled cooling of the head membrane 4 is performed by introducing of preferably sterile-filtered and low-particle cooling air as a cooling medium into the space between the insulation bodies 8 b and 8 c above the head membrane 4 via symmetrically arranged cooling air inlet channels 13 b. The heated air is discharged via cooling air outlet ducts 13 a, which are shown in FIGS. 9, 11 and 12, just like the inlet channels 13 b. By supplying cooling air in a controlled manner, an advantageous surface temperature of the head diaphragm 4 of approx. 250° C. to 300° C. can be achieved for a short time during the operation of the IR radiating element 7 b. In contrast to the heating element 14 b for container 1, the heating element 14 a for the cap 5 is not actively cooled or flushed. In this way, heating of the inner surface of the cap 5 is ensured, which also results in a reduction of germs on this surface. 

1. A method for joining at least two plastic parts (1, 5) along a predeterminable common joining point using infrared radiation (IR), characterized in that each of the plastic parts (1, 5) to be joined is heated using infrared radiation at least along the joint by means of an assignable radiation source without touching the respective other plastic part (1, 5), that the respective one radiation source is operated independently and spatially separated from at least one further radiation source, that the radiation sources emit their respective infrared radiation to the individually assignable plastic part (1, 5) without contact and following the contour of the joint, and that the degree of heating by means of the respective infrared radiation is selected such that the joint is formed when the plastic parts (1, 5) are brought together.
 2. The method according to claim 1, characterized in that the joint is formed as a linear connecting seam and that the respective plastic parts (1, 5) are joined by applying a predeterminable contact pressure on these parts (1, 5).
 3. The method according to claim 1 or 2, characterized in that the respective radiation source is formed from an IR radiation element (7 a, 7 b) and that the IR radiation elements (7 a, 7 b) used are operated at different temperatures, preferably one element (7 a) at temperatures of 380° C. to 480° C., particularly preferably 400° C. to 450° C., and a respective other element (7 b) at temperatures of 450° C. to 600° C., particularly preferably 500° C. to 550° C., each at a heating time of the respective plastic part (1, 5) of 2 to 6 seconds, preferably approximately 4 seconds.
 4. The method according to any one of the preceding claims, characterized in that any heat-sensitive plastic parts (1, 5) are cooled by means of a cooling device (13 a, 13 b), preferably using a low-particle gas, particularly preferably using a low-particle and sterile-filtered gas as cooling medium.
 5. The method according to any one of the preceding claims, characterized in that at least one plastic part (1) is produced as a filled and closed container (1) by a blow-molding, filling and sealing process.
 6. The method according to any one of the preceding claims, characterized in that the filled container (1) is closed by a head membrane (4) and enclosed by a ring-shaped neck collar (2) at its neck part (3), which collar (2) is connected to a cap (5) placed on the container (1) on the side of its head membrane (4) and forming the one plastic part via a ring web (6) of the cap (5) along the connecting seam, whereas the container (1) is used as the other plastic part for the joining or welding process.
 7. The method according to any one of the preceding claims, characterized in that a preferred spacing between the ring web (6) of the cap (5) and one assigned IR radiation element (7 a) is selected to be between 0.2 mm and 0.6 mm and the spacing between the neck collar (2) of the container (1) and the other assigned radiation element (7 b) is selected to be between 0.4 mm and 0.8 mm.
 8. The method according to any one of the preceding claims, characterized in that the infrared radiation generated by the respective radiation sources, respectively radiation element (7 a, b), is radiated in a broadband and multidirectional manner.
 9. The method according to any one of the preceding claims, characterized in that the head membrane (4) of the container (1) is heated in a manner reducing the germ count and without melting for joining cap (5) and container (1).
 10. The method according to any one of the preceding claims, characterized in that the cap (5) is joined to the container (1) in a low-particle way by using different IR radiation sources or radiation elements (7 a, 7 b).
 11. A apparatus for performing a method according to one of claims 1 to 10, characterized in that the respective radiation source is formed by an IR radiation element (7 a, 7 b) arranged inside a respective heating element (14 a, 14 b) assigned, which follows the contour of an assignable plastic part (1, 5) to be irradiated without contact.
 12. The apparatus according to claim 11, characterized in that the respective radiation elements (7 a, 7 b) has at least two radiation surfaces (11 a, b, c, d, e) oriented differently from one another.
 13. The apparatus according to claim 11 or 12, characterized in that the radiating surfaces (11 a, b) of the one IR radiation element (7 a) provided for the cap (5) are arranged in parallel (11 b) to the direction the cap is attached and perpendicular (11 a) thereto.
 14. The apparatus according to any one of the claims 11 to 13, characterized in that the radiating surfaces (11 c, d, e) of the other IR radiation element (7 b), which is used for the neck collar (2) of the vertically positioned container (1), are arranged in parallel (11 d) to the longitudinal axis of the latter and horizontally (11 e) and having a third radiating surface (11 c) inclined at a radiation angle of preferably 45° thereto.
 15. The apparatus according to any one of the claims 11 to 14, characterized in that the individual radiating surfaces (11 a, b, c, d, e) of the two IR radiation elements (7 a, 7 b) extend continuously in an annular and concentric manner around their respective longitudinal axes.
 16. The apparatus according to any one of the claims 11 to 15, characterized in that the IR radiation element (7 b) provided for the neck collar (2) of the container (1) has a cooling device (12, 13 a, 13 b) to cool the head membrane (4) of the container (1) using cooling air, which can be supplied to a cooling chamber (12) above the head membrane (4), into which chamber (12) the head membrane (4) projects for cooling and/or heating the neck collar (2).
 17. The apparatus according to any one of the claims 11 to 16, characterized in that the heating element (14 b) comprising the IR radiation element (7 b) has at least additionally at least a holding and insulating device (8 a, 8 b), which has a minimum distance from the head membrane (4) of the container (1) of at least 5 mm, preferably at least 8 mm, and particularly preferably at least 10 mm.
 18. The apparatus according to any one of the claims 11 to 17, characterized in that the respective IR radiation elements (7 a, b) can be adjusted to the respectively assigned plastic part (1, 5) via an adjustment device and can be removed again after the heat treatment.
 19. A container (1), preferably produced by a blow molding, filling and sealing (BFS) process, which is connected to a cap (5) using a method according to any one of the claims 1 to 10 and/or an apparatus according to any one of the claims 11 to
 18. 